The knee joint comprises the interface between the distal end of the femur and the proximal end of the tibia. In a properly-functioning knee joint, medial and lateral condyles of the femur pivot smoothly along menisci attached to respective medial and lateral condyles of the tibia. When the knee joint is damaged, the natural bones and cartilage that form the joint may be unable to properly articulate, which can lead to joint pain and, in some cases, interfere with normal use of the joint.
In some situations, surgery is required to restore normal use of the joint and reduce pain. Depending upon the severity of the damage, the surgery may involve partially or completely replacing the joint with prosthetic components. During such knee replacement procedures, a surgeon resects damaged portions of the bone and cartilage, while attempting to leave healthy tissue intact. The surgeon then fits the healthy tissue with artificial prosthetic components designed to replace the resected tissue and restore proper knee joint operation.
Some knee replacement procedures, such as total knee arthroplasty (“TKA”), involve the resection of some or all of each of the medial and lateral condyles of both the femur and tibia and the removal of the fibro-cartilage menisci located at the femorotibial interface. A prosthetic femoral component, typically made of titanium or other strong, surgical-grade metal, is fitted and secured to the distal end of the femur to replace the resected portion of the femur. Similarly, a prosthetic tibial component, the base of which is also typically made of titanium or other suitable metal, is fitted and secured to the proximal end of the tibia to replace the resected portion of the tibia.
The upper surface of the tibial component may include a flat or slightly concave element constructed of plastic material designed to replicate the form and function of the medial and lateral menisci located at the interface of the femur and tibia. This meniscus replacement element provides a low-friction surface upon which the femoral prosthesis can pivot smoothly at the femorotibial interface. The meniscus replacement element may be provided as part of a tibial prosthetic system, whereby a metallic tibial base component (“base” portion) is permanently secured to the tibia and the meniscus replacement element (“insert” portion) is subsequently inserted and secured to the tibial base component. Such a system allows for the insert portion to be replaced without disturbing the base portion if, for example, the insert portion becomes worn over time.
In an effort to reduce post-operative pain and shorten recovery times, surgeons continue to develop techniques for reducing the biological impact that many surgical procedures—including knee replacement procedures—have on the human body. Such techniques, which are commonly referred to as “minimally-invasive” techniques, are aimed at limiting the amount of tissue disturbance during the surgical procedure. For knee replacement surgery, this typically involves reducing the length of incision and limiting the amount of disturbance (e.g., cutting, stretching, etc.) of the muscles surrounding the knee joint.
Although minimally-invasive techniques may significantly reduce the amount of pain and recovery time endured by the patient, some of these techniques may limit the ability of the surgeon to visually inspect certain areas of the surgical site. For example, as the size of the incision used to perform a knee replacement procedure decreases, the surgeon's ability to visually inspect the posterior of the completed replacement joint may also decrease. Consequently, during minimally-invasive procedures, surgeons are increasingly reliant on non-visual (e.g., tactile) methods for ensuring that the tibial prosthesis components are installed properly. Incomplete or misaligned insertion of a component (e.g., tibial implant portion within the tibial base portion) can lead to discomfort and instability of the replacement joint, thereby increasing the likelihood of the necessity of subsequent corrective surgery.
In addition to the trend toward minimally-invasive surgical techniques, there is also a trend toward reducing manufacturing costs associated with prosthetic components. Decreasing manufacturing costs typically involves decreasing, at least to some degree, the precision with which the dimensions of the components match the specified design dimensions. In many orthopedic prosthetic systems, however, multiple components must precisely and firmly engage one another to limit movement between the components, increase stability, and reduce long-term wear. As a result, as lower cost, less precise manufacturing techniques are employed in the manufacture of prosthetic components, orthopedic prosthetic systems must be adapted to ensure that stability and function of the joint are not unduly compromised.
For example, in a tibial prosthetic implant system, manufacturing errors at the engagement interface between the tibial insert portion and the tibial base portion can result in movement or vibration of the insert component within the base component. This movement can cause micro-abrasions on the insert component that release small fragments of plastic into the knee joint. These fragments can cause significant irritation of the joint and/or lead to premature wear of the insert component. What is needed, therefore, is a solution for controlling manufacturing costs without sacrificing implant performance due to decreased precision of the implant components.
The presently disclosed locking assembly for a tibial base component is directed to overcoming one or more of the problems set forth above and/or other problems in the art.